This investigation is a study of the effectiveness of iodized oil in reducing and preventing goiter and its attendant cretinism, deafmutism, and neurological disorders in rural Ecuador and Peru where endemic goiter is severe and protein intake is low. Prophylaxis with iodized oil has already begun. It is necessary to measure the long term effects of this program in terms of changes in thyroid function and in child growth and development. Effectiveness is measured in terms of reduction in goiter size and the incidence of defective children born into the program, compared to control groups. Fetal-maternal thyroid relationships are measured in terms of standard measures of thyroid function, excepting those involving radioactive material, in pregnant women and at the time of delivery. Neurological observations include developmental milestones, audiometry, EEG, and intellectual growth. This investigation also includes a study of the effects of adding lysine and tryptophan supplements to the daily diet in order to increase the availability of the maize protein which constitutes the chief dietary source. The results of this will be measured in terms of prematurity rate, perinatal mortality, and early growth and development. This part of the study is designed so that interactions between iodine supplementation and protein supplementation can be ascertained.